In order to determine the depth to the water table, available groundwater levels from unconfined areas (cf. Map 02.12 Groundwater Levels of the Main Aquifer and Panke Valley Aquifer 2020) and the triangulated irregular network method were used to calculate a uniform groundwater surface grid. The triangulated irregular network may be used to model surfaces based on a point cloud (mass points). In order to model the surfaces, mass points are connected to a triangle mesh, forming a network structure: the groundwater surface values are then subtracted from those of the terrain elevation to determine the depth to the water table based on a grid width of 1 metre.
For areas with confined groundwater, the depth to the water table is defined as the difference between the lower edge of the overburden (or the upper edge of the groundwater aquifer) and the ground level. For these areas, a grid dataset was therefore calculated for the lower edge of the overburden, corresponding to the height of the groundwater surface in confined groundwater conditions.In addition, there are areas in the north of Berlin (Märkisches Viertel, Lübars, Blankenfelde, Rosenthal and between Gesundbrunnen and Prenzlauer Berg) where the quaternary main aquifer covered by boulder marl is not widespread but only occurs in isolated places. Water seeping into the subsoil here usually does not reach the aquifer. Instead, the water flows laterally to the nearest tributaries, atop cohesive connecting layers near the surface (also called “hypodermic runoff”). Due to the complexity of the retention conditions in such areas, they were not included in the calculations (light grey areas in the map).Subsequently, the two grid datasets for the unconfined and confined areas were merged in order to create a depth to groundwater dataset for the whole of Berlin.
The depth to groundwater was categorised into 14 classes and shown as strata on the map. For more differentiated information, especially for areas near the surface, a small-scale classification was chosen up to a depth of 4 metres below ground level.
It should be noted that the groundwater surface in the vicinity of production wells is subject to strong fluctuations depending on the pumping rate. For this reason, varying depths to groundwater may occur here, the extent of which cannot be displayed at the selected scale.